The corrosion resistance of a metal strip can be enhanced by coating the strip with molten metal, such as zinc. It has been known to anneal the metal strip, prepare the surface of the metal strip for coating in a protective atmosphere maintained in an enclosure, and then immerse the metal strip in a bath of molten metal to coat the metal strip with the molten metal.
Immersion baths may not guarantee consistent product quality of the metal strip. For example, changes in the surface condition of pot rolls directing the metal strip through the bath can cause negative effects on the metal strip such as marks or scratches, as well as nonuniform coating thickness formation. Further, immersion bath methods often require a large molten metal reservoir that, with the pot rolls, is costly to manufacture and maintain.
Meniscus coating methods are known, as disclosed in U.S. Pat. No. 5,453,127, entitled “Apparatus for Meniscus Coating a Metal strip,” issued Sep. 26, 1995, and U.S. Pat. No. 5,399,376, entitled “Meniscus Coating Metal strip,” issued Mar. 21, 1995, which patents are incorporated by reference herein. The metal strip is treated (for example, the metal strip is heated in a furnace, or heated and cooled, to achieve a temperature near a melting point of a coating metal prior to the metal strip being coated with the coating metal). After such treatment, the metal strip passes through a protective, often non-oxidizing, atmosphere contained within an enclosure to arrive at a coating tray holding a pool of molten coating metal. The metal strip typically passes close to the pool of molten metal and surface tension bridges the gap between the molten metal surface and the metal strip, allowing the molten metal to coat the strip.
The present application describes a meniscus coating apparatus that provides for coating of the strip outside of the protective enclosure by minimizing the ingress of ambient air into the enclosure containing the protective atmosphere.
The drawings are not intended to be limiting in any way, and it is contemplated that various embodiments of the invention may be carried out in a variety of other ways, including those not necessarily depicted in the drawings. The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention; it being understood, however, that this invention is not limited to the precise arrangements shown.